Watching in the Dark
There was something sort of ritualistic about television
watching when I was young. My family's first set was delivered the day before Queen
Elizabeth's coronation in 1953, and we spent the big day staring at this altar to mass
communications. The event itself was remarkable enough: the ceremonies were filmed in
London earlier that day and flown to Halifax, Nova Scotia to be fed into the North
American TV system, the film having been developed in the air over the Atlantic.
But what I remember most clearly was the whole bunch of us
sitting inside on a beautiful late spring day in an almost pitch-black room. Those early
sets were very dim, and so to see anything you had to make the room very dark. That wasn't
too much of a problem in the evening -- just turn a few lights off -- but daytime viewing
called for heavy curtains to keep the light out. And still the picture was dim.
From the earliest days, therefore, picture-tube
manufacturers worked at improving phosphors to produce an image bright enough that you
could watch it during the day, or at night in a room with some lights on.
That the effort was successful is witnessed by the fact
that we rarely think about the lighting in our viewing rooms, at least if our sets are
conventional CRT direct-view models. Even many projection TVs are bright enough today to
watch in a fairly well-lit room.
But technical purists tell us that we had the right idea in
the first place, and that most of us watch a picture that is far too bright to be
realistic.
Once you have cranked the brightness to the point where it
overcomes the effects of ambient light, and adjusted the contrast (or "picture")
to restore good blacks rather than washed-out grays, you have to set the color levels very
high to establish a reasonable balance among the various picture elements. Otherwise the
result is pastel-like hues.
These adjustments can make for pleasing and dramatic
colors, but they are far from accurate. Think of what a piece of movie film looks like in
a theater, or the color photographs you took on your last vacation, and you'll soon
appreciate the exaggerated cartoon-like colors we are routinely offered by our television
monitors.
Not only is the color affected. When we bombard the
phosphors on the inside of the TV screen with enough electrons to achieve a satisfying
brightness, we also sacrifice sharpness. The over-stimulated phosphor granules can affect
their neighbors, which blur the lines between light and dark areas.
In evaluating television monitors, reviewers generally run
the set at the factory default settings and feed it a resolution test pattern: a series of
calibrated converging lines that indicate maximum sharpness. Where the lines blur together
is just beyond that maximum. Once we note the resolution with the default settings, we
gradually turn down the brightness and watch the numbers rise; the difference can be as
much as 20 or 30 lines.
The interests of good video fidelity would thus probably be
best served by our watching at lower levels. Movie theaters are dark because films are
dark, and anyone who has ever visited a TV-station control room has noticed the very low
ambient light levels.
In fact, there is a standard brightness for professional
video monitors (6500-degrees Kelvin, if you care), and it's surprisingly dark. Yet one of
the things that have to be established for a video transfer to qualify as THX-Certified is
that the monitor used be calibrated to this level.
You can't just dial that up on your new set; it needs
sophisticated measuring devices to get all of the picture parameters right. And there's
even some doubt that many home monitors can even be made to go that dim at all. But there
are approximations that can be useful.
One set I examined recently offered a "cinema"
mode that was significantly darker than the regular mode (although the company made no
claim to its meeting the 6500-degree standard). It looked very peculiar at first, but we
decided to live with it for a while to see whether it was really any better.
Frankly, I was surprised at how quickly I got used to the
lower level. And once the other picture characteristics had been adjusted, I had to admit
that the picture quality was excellent and somehow "theatrical." And with the
right signal source -- DVD or a really good off-air program -- the image had a wonderful
snap.
But do I watch this way as a matter of routine? Nope.
For one thing, it's too inconvenient. I like to be able to
see people in the room with me as I watch, and to be able to read the TV listings without
a flashlight. And however purist I might want to be, it will never be practical to watch
such dim images during the daytime in my room, which is dark but not black.
In any event, the benefits tend to be evident only with a
pristine signal source rather than the sort of run-of-the-mill stuff we often watch --
don't expect to notice any difference at all if you're watching a filmed sitcom or a
videocassette.
It makes sense to use calibrated monitors to master a video
program, to make sure the very best picture is on the disc or tape. But thanks; I'll leave
the Stygian gloom to the pros. I prefer a bit of light.
...Ian G. Masters
ian@mastersonaudio.com
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